DESCRIPTION: (Applicant's Abstract) Phase I of the proposed project will examine barriers to comprehensive HIV and other infectious disease testing and follow-up care among substance abusers at a short term (detox) substance abuse treatment center. In Phase II an intervention that includes comprehensive testing, counseling, medical deferral, and practical strategies to overcome barriers to follow up care will be designed and pilot tested. During Phase III, the intervention will be evaluated against the standard of care of offering HIV testing done through a randomized controlled trial. Three hundred and forty-four participants will be randomized to receive either the comprehensive testing and facilitated referral intervention which will offer testing for HIV, hepatitis B and C, and the STDs gonorrhea and chlamydia (and trichomonas for women only) or standard of care HIV testing alone and referral for further hepatitis and STD testing. Primary endpoints will be the number of tests performed, the number of test results received, and the degree of follow up medical care obtained for the two groups.